1. Field of the Invention
The present invention relates to a transaxle having a hydrostatic stepless transmission (hereafter, referred to as “HST”) therein, the HST being constructed by fluidly connecting a hydraulic pump with a hydraulic motor.
2. Related Art
As disclosed in U.S. Pat. Nos. 6,508,059 and 6,682,453, conventionally, there is a well-known transaxle called as “IHT” (integral hydrostatic transaxle) comprising a housing incorporating an HST and an axle drivingly connected to the HST. The HST includes mutually fluidly connected hydraulic pump and motor.
In the transaxle of the U.S. Pat. No. '059, a motor shaft of a hydraulic motor, axles, and a counter shaft constituting a deceleration gear train interposed between the motor shaft and the axles are disposed horizontally in parallel, and are sandwiched between extended parts of upper and lower housing elements through respective bearing bushes. Since mutually meshing gears are disposed on the shafts and axles, alignment (axial location) of the shafts and axles in the housing of the transaxle requires high accuracy, thereby requiring highly elaborate and expensive processing of the housing. Furthermore, both the upper and lower housing elements requires elaboration in processing to sandwich the shafts and axles therebetween and to be joined to each other. Therefore, it is desirable for easing assembly of the transaxle and reducing cost thereof to ensure efficient and accurate alignment of the shafts with easy construction of the housing.
Moreover, with regard to the transaxle of the U.S. Pat. No. '059, the HST is immersed in an oil sump in the housing. A center section of the HST is formed at the bottom thereof with a charge port opened to the oil sump, and an oil filter for filtering oil to the charge port is sandwiched between the bottom surface of the center section and the housing. The oil filter requires sure oil sealing between the oil filter and the bottom surface of the center section or between the oil filter and the housing. An oil seal disclosed in the U.S. Pat. No. '059 is just sandwiched between the oil filter and the bottom surface of the center section, and is not engaged integrally with the oil filter, thereby complicating assembling thereof. If the oil filter has an oil seal previously fitted thereto, labor for the assembly is reduced so as to reduce the cost.
Furthermore, with regard to the U.S. Pat. No. '059, a brake disc is provided at the tip of the motor shaft of the hydraulic motor, and a brake mechanism is provided in the housing so as to brake the brake disc. An arm for actuating a cam of the brake mechanism is disposed out of the housing and pivotally supported on a wall of the housing. The arm is switched between a braking position and a braking-off position, and at each position, the arm is fixed by a stopper provided near the arm. The arm is biased toward the braking-off position by a spring or the like. However, the positional relation between the braking position and the braking-off position becomes different according to difference of transaxles. Therefore, it is necessary to change the position and structure of the stopper and spring following the difference of the positional relation. Standardization of attachment structure of the brake arm regardless of different positional relation between the braking position and the braking-off position is desirable for reducing the parts count and cost.